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2009 YZ450 won't stay running after it warms up

By pastranafan5,
in YZ400F/426F/450F/450FX

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x_JT_x

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I just bought this bike and it starts and runs fine when it is cold, but after it warms up it won't stay running. It starts right up, but either dies right away or after several seconds. Does anybody have any thoughts on this?

Is it acting like its starving for fuel? Or like its got a problem in the Engine?

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Treeyz450

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It could possibly be the stator. I just read a thread about this on the same year. The owner even bought an aftermarket stator, but after a lot of troubleshooting, he found that it was putting out a little too much, so he put an OEM one in and it ran fine.

Hope this helps

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torkd14

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My '06 started doing that after putting a LEXX muffler on. The pipe was to restrictive with the spark arrester in and would cause the bike to die. You can either re-jet or in my case i just pulled the arrester out. I think you just have to do some jetting but im sure Greyracer will chime in with the proper fix. 

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Treeyz450

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Like the kill switch, but instantly. It's never hard to kick, and always starts easy.

Ok, the only reason I asked is because my 08 450 used to just die, then it would be physically hard to kick, but when I got it to turn over, it was fine again. Then it would start and run for a little bit, then do it again. Come to find out, it was my main rod bearing.
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Dexter42

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I too would lean towards the stator or bad connection/ ground somewhere. Remove the tank and seat and just make sure all connections/ grounds are connected properly, no water in the sparkplug pocket, and if you have a multimeter it's really not that bad to check the stator. The manual will give you ohms reading it should be putting out and you tube will make it easy to identify what your trying to accomplish. You get a manual?

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Treeyz450

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I too would lean towards the stator or bad connection/ ground somewhere. Remove the tank and seat and just make sure all connections/ grounds are connected properly, no water in the sparkplug pocket, and if you have a multimeter it's really not that bad to check the stator. The manual will give you ohms reading it should be putting out and you tube will make it easy to identify what your trying to accomplish. You get a manual?

+1...........like he said, check with a meter, then if they are reading right, get some electric contact cleaner, and clean all connections, and put a little dielectric grease on the connectors, then at least you know you have good connections.
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jrice2012

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I just bought this bike and it starts and runs fine when it is cold, but after it warms up it won't stay running. It starts right up, but either dies right away or after several seconds. Does anybody have any thoughts on this?

By any chance did you buy this from a guy in Mississippi? My friend just sold his with it having this problem.

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pastranafan5

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I too would lean towards the stator or bad connection/ ground somewhere. Remove the tank and seat and just make sure all connections/ grounds are connected properly, no water in the sparkplug pocket, and if you have a multimeter it's really not that bad to check the stator. The manual will give you ohms reading it should be putting out and you tube will make it easy to identify what your trying to accomplish. You get a manual?

 

+1...........like he said, check with a meter, then if they are reading right, get some electric contact cleaner, and clean all connections, and put a little dielectric grease on the connectors, then at least you know you have good connections.

I have a manual. I'm gonna try that and see what happens. So y'all don't think the pilot jet being a 52 instead of a 45 would cause it? Or maybe bad orings inside the carb?

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Treeyz450

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I have a manual. I'm gonna try that and see what happens. So y'all don't think the pilot jet being a 52 instead of a 45 would cause it? Or maybe bad orings inside the carb?

I think if it is a problem with the pilot jet, it would have problems from the get go not just when it warms up. It would be a problem the whole time. I would definitely take the carb apart, clean it, and check based on your Elevation and make sure the right Jets are in it. do you have to use the choke to get it started? Do you have to leave the choke on or off to keep it running?
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pastranafan5

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I think if it is a problem with the pilot jet, it would have problems from the get go not just when it warms up. It would be a problem the whole time. I would definitely take the carb apart, clean it, and check based on your Elevation and make sure the right Jets are in it. do you have to use the choke to get it started? Do you have to leave the choke on or off to keep it running?

I've cleaned it and put a 45 pilot jet in it and it seemed to be fine, except for running a little rough, but it was cold outside so I was gonna wait till it warmed up to see if it changes. I only have to use the choke when the engine is cold. Once it warms up it starts and runs without it. Would the stator not cause problems when it's cold also?

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grayracer513

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The stator can cause trouble only when hot, if the failure is of the right nature.  It can be a matter of the resistance increasing with temperature, which is a normal phenomena that might put the values out of spec under certain conditions, but more likely a transient open connection that butts up against itself well enough to make good contact when cooler, but opens when the coil gets hot.  Test the stator while it's acting up, and also try rapping on the stator cover with a wood hammer handle, etc., to see if that makes the meter bounce around.

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pastranafan5

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The stator can cause trouble only when hot, if the failure is of the right nature. It can be a matter of the resistance increasing with temperature, which is a normal phenomena that might put the values out of spec under certain conditions, but more likely a transient open connection that butts up against itself well enough to make good contact when cooler, but opens when the coil gets hot. Test the stator while it's acting up, and also try rapping on the stator cover with a wood hammer handle, etc., to see if that makes the meter bounce around.

I'll try that. If that's the problem though, why would it start right back up? Wouldn't it not start until it cools off?
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